Long travel hydraulic cushion device



May 10, v1966 w. H. PETERscN LONG TRAVEL HYDRAULIC CUSHION DEVICE Filed May 1, 1964 5 Sheets-Sheet 1 uNvENToR WILLIAM H. PETERSON May 10, 1966 w. H. PETERSON LONG TRAVEL HYDRAULIC CUSHION DEVICE vFiled May 1, 1964 Sheets-Sheet 2 :NVENTOR WILLIAM H. PETERSGN BY fdd? ATTY.

May 10, 1966 w. H. PETERSQN LONG TRAVEL HYDRAULIC CUSHION DEVICE 5 Sheets-Sheet 5 Filed May l, 1964 fw Ilh mmf w \wm 7/ M A v/ um, /A// ../////il V V// ERSON ATTY.

May 10, 1966 Filed May l, 1964 W. H. PETERSON LONG TRAVEL HYDRAULIC CUSHION DEVICE 4; ,wir f }\\\\\\\\\IHT 5 Sheets-Sheet 4 INVENTOR WILLIAM H. PETERSON May 10, 1966 w. H. PE'rx-:RsoN

LONG TRAVEL HYDRAULIC CUSHION DEVICE 5 sheets-sheet 5 L Filed May l, 1964 N .Null Amm/MN MN h A///////// NW INVENTOR WILLIAM H. PETERSDN ATT'Y.

United States Patent() 3,258.525 LNG TRAVEL HYDRAULIC CUSHIGN DEVICE William H. Peterson, Homewood, Ill., assigner to Pullman Incorporated. Chicago, lll.. a corporation of Delaware Filed May 1, 1964. Ser. No. 34,1S5 9 Claims. (Cl. 267-1) The present invention relates to hydraulic cushion devices which may be employed in cushion underframe railway vehicles and more particularly to a hydraulic cushion device of the type having a flexible boot reservoir for receiving hydraulic fluid displaced during the cushioning travel thereof.

The hydraulic cushion of the type to which the present invention relates comprises generally a hydraulic fluid filled cylinder and a iluid displacement means which is operative upon impact to either or both the fluid displacement means or the cylinder to reciprocate between a neutral extended position and a contracted position. During the relative movement the hydraulic iluid within the cylinder is displaced therein from a high pressure chamber to a low pressure chamber.

In order to provide a construction utilizing solely static seals, an expandable flexible reservoir boot is asociated with the low pressure chamber for receiving the displaced fluid. In the neutral position of the cushion device, the ileXible boot reservoir is substantially deiiated and devoid of hydraulic fluid and upon contraction of lthe unit the displaced hydraulic fluid causes the boot to expand and become inilatecl. During the return travel of the unit from the contracted position the hydraulic iluid ilow is reversed such that the boot is again deated. Under normal conditions of operations the volumes of hydraulic uid are returned to fill the volumes provided by the cushion unit in the neutral position. However, under some conditions of impact, the return travel -time of the unit from the contracted to the extended position may be greatly accelerated. When accelerated the construction of the cushion devices as employed heretofore were such that the return or reverse hydraulic iluid flow to the initial position, that is to the high pressure chamber was retarded. This retarded ilow condition resulted in the formation of a vacuum in the high pressure chamber in front of the moving piston head and an increase in pressure forces behind the head of the low pressure chamber. Due to the high pressure forces within the low pressure chamber the hydraulic :fluid rather than leaving the flexible boot reservoir was forced to remain therein and additional iluid entered. This caused the flexible boot to expand beyond its designed capacity and bulge outwardly of the cushion unit and under some circumstances to burst or cause malfunctioning of the unit.

It is obvious with a vacuum present in the high pressure chamber that should an impact be applied before the iluid filled the vacuum the resulting resisting force would be greatly diminished so that the overall efficiency of the cushion unit would be greatly diminished.

It is a principal object of the present invention to provide a new and improved cushion device which overcomes the difficulties encountered heretofore with the rupturing of the exible boot reservoir or maliunctioning of the cushion device.

yIt is another object to provide a new and improved cushion device with an arrangement for precluding the return ilow of hydraulic iluid into the flexible boot during the travel of the device from the contracted to the neutral position.

lt is still another object to provide a new and improved cushion device with an arrangement for precluding the return llow of hydraulic fluid into the flexible '-boot during the travel of the device from the contracted to the neu- 3,250,525 Patented May l0, 1966 tra] position and also with means for preventing a vacuum from being formed in the high pressure chamber.

Further objects and features will hereinafter appear.

In the drawings:

FIG. 1 is a fragmentary cross-sectional view of a hydraulic cushioning device embodying the present invention and showing the components of the unit in the neutral extended position;

FIG. 2 is a fragmentary cross-sectional view similar to FIG. 1, but showing the components of the cushion device in the contracted position which is assumed upon impact;

FIG. 3 is an enlarged fragmentary cross-sectional view of the cylinder and the lluid displacement means taken in the vicinity of the intermediate cylinder head and showing the relative positions of the components of the cushion unit and the reverse flow arrangement during the initial portion of the travel from the neutral to the contracted positions;

FIG. 4 is an enlarged fragmentary cross-sectional view similar to FIG. 3 but showing the components of the cushion unit and the reverse iloW arrangement during the return travel of the cushion unit from the contracted -to neutral position;

FIG. 5 is an enlarged fragmentary cross-sectional view similar to FIG. 3, but showing another embodiment of reverse ilow arrangement and showing the relative positions of the cushion device during the initial travel from the neutral to contracted positions;

FIG. 6 is a front elevational view of the valve disc employed in the reverse flow arrangement of FIG. 5;

FIG. 7 is an enlarged fragmentary view similar to FIG. 5 showing the components during the reverse travel thereof;

FIG. 8 is a cross-sectional view taken generally along the lines 8-8 of FIG. 7.

Referring now to the figures there is shown a hydraulic cushion unit 19 comprising essentially a hydraulic fluid lled cylinder 11, a fluid displacement means 12 which upon impact to the unit is reciprocal relative to the cylinder 11 from a neutral position to a contracted position for displacing fluid from a high pressure chamber 13 to a low pressure chamber 14, a ilexible boot reservoir 15 connected between the cylinder 11 and the fluid displacement means 12 for receiving hydraulic fluid displaced during the contraction of the unit, a metering pin 16 for metering the ilo-w between the high pressure chamber 14 and the high pressure chamber 13, 'a return spring means 17 for returning the fluid displacement means 12 and the cylinder 11 to the neutral position after the force of impact causing the contraction has been dissipated.

In accordance with the present invention the cushion device 10 is provided With a reverse ilow arrangement 18 for preventing the flow of the hydraulic lluid back into the flexible boot reservoir 15 during the return travel of the cushion device 10 from the contracted to neutral positions. There is also incorporated into the unit a pressure relief arrangement 19 for assuring adequate reverse ilow between the low pressure chamber 14 and the high pressure chamber 13 during the return travel of the cushion unit 10 to preclude the formation ot' a vacuum inthe high pressure chamber.

As shown, in particular in FIGS. 1 and 2, the cylinder 11 is formed from a cylindrical tube 20 made from steel or the like. Fixed as by welding, to one end of the tube 20 is a base or follower plate 21 which extends beyond the outer circumference of the tube 20 to provide a spring retaining ledge which accommodates one end of the return spring means 17.

Fixed within the cylinder bore 22 is an intermediate cylinder head 23 which denes the inner end of the boot 3 chamber 24 and accommodates the flexible boot 15. The intermediate cylinder head 23 is suitably fastened within the cylinder bore 22 by means of snap rings 25. A seal is formed at the bore wall by a quadrant ring 26.

The fluid displacement means 12 includes a piston head 27 which may be suitably made from cast iron or the like. The piston head 27 defines on one side thereof with the follower plate 21, the high pressure chamber 13 and on the opposite s ide thereof with the intermediate cylinder head the low pressure chamber 14. Forming a seal at the periphery of the piston head is a guiding ring 28 which is preferably formed of a laminated phenolic resin.

As shown, the forward or high pressure face 29 of the piston head 27 is formed with a circular recess 30 having a substantially planer bottom wall 31 from which there extends a rearwardly directed frnstrom of a cone feed surface 32. The feed surface 32 merges with a rim 33 of an axial orifice 34 formed through 4the piston head 27.

Fixed to the rearward or low pressure face 60 of the piston head 27 is one end of a tubular piston rod 36 having a bore 37 which is axially aligned with the orifice 34. The Vtubular piston rod 36 extends outwardly through an axial opening 38 formed in the intermediate cylinder head 23 and defines therewith an annular passage 39 which provides hydraulic fluid communication between the low -pressure chamber 14 and the flexible boot reservoir 15.

Fixed to the outer end of the piston rod is a second base plate 40 which may be attached by way of a fastening bolt threaded into a fastening block fixed within the piston rod bore 37.

The fiexible boot reservoir 15 may be formed from a suitable flexible and resilient material which is fluid impervious, as for example, rubber. The boot 15 is connected at one end to a boss 41 formed on the outer face of the intermediate cylinder head by means of a hose clamp 42. At the other end, the boot 15 is reversely turned and the reverse end is clamped to the piston rod 36 also by means of a hose clamp 42.

As was shown in FIG. 1, in the extended or neutral position of the hydraulic cushion device, the boot 15 is defiated and'substantially devoid of hydraulic fluid, but in the contracted position the boot 15 is contracted and inflated by the hydraulic fiuid which is displaced during the contraction thereof as more fully to be explained hereinafter. It is to be noted that as shown in FIG. 2 the boot 15 is designed to occupy substantially the complete volume of the annular boot chamber 24 when inated by the displaced hydraulic fluid.

Providing communication'between the piston rod bore 37 and the low pressurechamber 14 are an array of ports 43 which are located adjacent to the piston head 27.

Fastened to the base plate 21 and coaxially extending through the piston head orifice 34 is the metering pin 16 which serves to control the flow of the hydraulic fluidv from the high pressure chamber 13 to the low pressure chamber 14. Preferably, the hydraulic flow between the high and low pressure chambers 13 and 14, respectively, is such as to impart an approximately constant force travel characteristic to the cushion unit during the contraction thereof., To this end, the pin formed of substantially constant diameter along the. length thereof and be noted that the total effective cross-sectional orifice area is at a maximum in the extended or neutral position permitting a maximum How therethrough and the effective cross-sectional area gradually decreases to a minimum at the end of the travel lto gradually cut off substantially any of the ow between the high and low pressure chambers 13 and 14 at the end of the stroke.

Disposed between the base plates 2 1 and 40 is the return spring means 17 which in the form shown may be a plurality of strings 17a, 17b and 17c arranged in tandem. VAs heretofore described, in the contracted position of the cushion device \10 the metering pin 16 and the piston head 27 are positioned relatively to each other so that substantially all hydraulicow of the fiuid is cutv off through the flutes 44 and the orifice 34. It is-only after the return travel of the cylinder 11 and fluid displacement means 12 has been initiated that hydraulic fluid flows through the orifice 34 and the flutes 44 and then lengthwise extending flutes 44 of varying depth are formed along the periphery of the metering pin to vary the effective area of the orifice 34 through which the hydraulic fiuid flows during the contraction and extension of the unit.

The flutes 44 are formed to cooperate with the piston head orifice 34 in a manner which maintains the pressure forces within the high pressure chamber 13 approximately constant during each increment of relative movement between the piston head 27 and the cylinder 11.` This is accomplished by varying the effective orifice area through the rim 33 in accordance with the total crosssection area of the flutes 44. In this connection it is to only at a gradually increasing rate. Under some circumstances of impact encountered in train operation, the irnpacts occur in a rapid buff and draft sequence. sequence of impact causes `the return travel of the cushion device to be rapidly accelerated yand far more rapidly than the hydraulic fluid is able to ow through the restricted effective orifice area as defined |by the rim 33 and the flutes 44. I n the absence of an adequate flow hydraulic fluid through the orifice 34 a vacuum may be created in `front of the moving piston head 27 in the high pressure chamber 13. At the same time an excessive quantity of iiuid remains within the low pressure charnber 14. The excessive fiuid within the low pressure chamber .14 may create excessive pressure forces behind the head 27 which tend to cause the hydraulic iiuid to reenter the exitble boot 15 by Way of the annular passage 39. Such re-entry of the hydraulic fluid into the boot 15 during the return travel tends to expand the boot beyond its design capacity so that it bulges outwardly off the boot chamber y24. When the boot is thus bulged the latter may become entangled within the return springs 17a, l1713 and17c to cause malfunctioning of the unit 10 or even under some circumstances burst-the boot.

In accordance with the present invention the over-expansion or bulging of the flexible boot 15 during the return travelis prevented by the valving arrangement 45 which is operative to cut off substantial flow into the boot 15 during the return travel as more fully to be explained hereinafter. FIGS. 1 Ito 5, the valving arrangement 45 comprises ygenerally an elongated cylinder 46 which is fixed at one end to the inner face of the intermediate cylinder head 23 and arranged coaxiallywith the tubular piston rod 36. The cylinder 46 forms an extension 47 of the annular passage 39 and communicates at its other end with an enlarged valve chamber 48 having a plurality of angularly spaced ports 49.

lFixed Within the valve chamber 48, intermediate of the ends thereof is an annular valve pla-te 50 lwhich seats within a groove 511'and is held fixed by means of a snap ring 52. As shown, the annular valve plate 50 is for-med with an axial opening 6l1 substantially equal to the :inner diameter of the cylinder 4 6. Slidably disposed between the end of the cylinder 46 and the inner surface of the stop valve plate 50 is an annular slidable valve disc 53 having a recess grove 54 formed about the annular opening 55a. Seated within the recess groove 54 is a` plurality of L-shaped spring fingers 5-5 of which the horizontal legs 56 resiliently embrace the outer periphery of thetu'bular piston rod 36 and the vertical legs 57 abut the vertical 'wall of the recess 54. Fixing the vertical legs to the valve discs are rivets 58. The spring fingers 55 are adjusted to permit sliding movement between the position shown in FIG. 3 land the position of FIG. 4 in which latter position the rear face of the valve disc 59 overlies the annular passage extension 39a so This I As shown in the embodiment of as to preclude the re-entry of duid into the tiexible boot reservoir 15.

vIn the neutral position as shown in FIGS. 1 and 3 it is to be noted that the array of ports 43 adjacent the piston head 27 to the tubular piston rod 36 are disposed for communication with the annular chamber 39 and annular extension 47. This arrangement permits the valve disc to utilize the pressure forces of thehydraulic fluid flowing through the array of ports 43 into the annular extension 47 displacing the disc to the position shown in FIG. 3 as more fully to be described hereinafter.

The pressure relief arrangement 19 comprises a plurality of angularly spaced relief ports 59 extending through the piston head 27 `from the low pressure face 6d to the bottom wall 31 of the piston head circular recess 30. Disposed within the circular recess 30 and movable from a position overlying the relief ports 59 to a position clear thereof is an annular valve member 62. Limiting the movement of the valve member 62 within the circular recess 30 is a snap or stop ring 63 which is spaced outwardly of the bottom wall 31. It is to be noted that the relief ports 59 communicate with the enlarged valve chamber 48 of the reverse flow arrangement 18.

During the contraction or compression stroke of the cushion unit as the valve member 62 is pressed into seal ing engagement on the face '31 over the openings 59 by the pressure forces of the hydraulic uid acting thereon in the high pressure chamber 13. During the return travel the pressure forces within the low pressure chamber 14 which are greater than those present in the high pressure chamber 13 are operative to displace the valve member 62 from the superposed position over the relief ports 59 and slide the valve member 62 lengthwise against the stop or snap ring 63 clear of the relief ports 59.

In operation the cushion device of the present invention may be disposed for interaction between the sliding sill and the stationary sill of a cushion underframe railway vehicle (not shown). When thus disposed the cushion device 10 assu-mes the position shown in FIG. l in the neutral position. Assuming an impact at one end of the sliding sill, the force of impact causes the sliding sill to move relatively to the underframe.

The cushion device 10 disposed therebetween is simultane-- ously actuated and the piston head 27 and the base plate 211 move toward each other whereupon the metering pin 16 fixed to the latter displaces hydraulic fluid within the piston rod bore 37 outwardly through the array of ports 43 and into the annular chamber extension 47.

The hydraulic liuid is forced longitudinally outwardly toward the eniarged valve chamber 48 and toward the iiexible boot 15. The force of the fluid and the acting on the face of the valve disc 53 forces the latter toward the right and at the same time the friction fingers 55 are also operative to carry the valve disc 53 along with the piston rod 36 which is moving in the same direction toward the valve plate 52. Thus, during the contraction stroke the annular valve disc 53 assumes the position shown in FIG. 3 overlying the annular passage 61.

At the same time hydraulic duid displaced from the high pressure chamber 13 flows through the gradually decreasing orifice area at the piston head orifice 34 and into the piston rod bore 37 from whence it flows initially into the low pressure chamber 14 and boot 15 via the array of ports 43, the ports 49 and annular .passages 39 and 47. When the array of ports clears the chamber 48, the hydraulic uid liows directly into the low pressure chamber 14 from whence its flows into the boot via ports 49 and annular passages 39 and 47.

The hydraulic liuidV is discharged into the low pressure chamber 14 at a relatively high velocity and creates a considerable turbulence therein. The turbulence is caused at least in part by the radially directed flow of hydraulic uid impinging directly against the inner wall of the cyl- 5 inder 11 so as to dissipate some of the kinetic energy of the impact in the form of heat.

When the cushion has completed its travel the cushion device 10 is then fully compressed and the metering pin 16 and the piston head 27 are located relatively to each other such that the latter lie somewhat beyond the ends of the utes 44. In this position of the piston head 27 and the metering pin 16 substantially all hydraulic fluid ow is cutoff through the piston head orifice 34.

Normally, in the absence of a :sharp impact on the opposite direction from that causing the contraction, the return spring means 17a, 1712 and 17C acting between the base plates 21 and'4l) is operative to extend the cushion device 1t) to its neutral position, whereupon the base plate in engagement with sliding sill is also Voperative to return the latter to its neutral position. During the return travel of the cushion unit to the neutral position as shown in FIG. 2 the flow of the hydraulic uid is reversed and the initial volumes are again filled with hydraulic uid such that the cushion device is again operative to perform its energy absorbing function. In the absence of -an impact in direction of return travel the weight of the sliding sill acting against the cushion device is suicient to retard the force of the return spring so that there is adequate time for the uid to fill the volume of the high pressure chamber 13 through the piston orifice 34. However, in the event that a shock impact is applied inthe same direction as that of the return travel, such that the weight of the sliding sill is no longer resisting the cushion device return spring, the return travel is greatly accelerated. It is under these circumstances that the reverse flow arrangement and the pressure relief arrangements 18 and 19 are operative to perform their functions effectively.

During the return travel from the contracted position shown in FIG.. 2 and FIG. 4 to the neutral position shown in FIG. 1 and FIG. 3, the valve disc member 53 which is frictionally held against the tubular piston rod 36 by means of the spring fingers 56 moves with the latter towards the left as viewed in FIGS. 2 and 4. Thus, the rear valve seat face seats against the end of the cylinder 46 so as to cut-off substantially any fluid iiow through the annular passages 47 and 39 from the low pressure chamber 14. It is to be noted that the annular opening of the valve disc 53 is somewhat greater than the outer diameter of the tubular piston rod 36 so as to permit a slight seepage of fluid therethrough. Under some conditions this may permit some of the hydraulic fluid flowing from Ithe liexible boot reservoir 15 through the passages 39 and 47 to seep very slowly between the space provided between the rim of the disc and outer circumference of the tubular piston rod 37. Such a flow, if any, will be very slow and a substantial reverse liow from the low pressure chamber 14 to the flexible boot 15 is substantially precluded. Thus it is readily apparent that the annular valve member 50 is operative to preclude the reverse flow of the hydraulic liuid into the boot chamber 15.

At the same time the pressure forces of the hydraulic` uid within the low pressure chamber 14 behind the moving piston head is applied through the relief ports 59 on to the valve disc 62 to unseat the latter from overlying relationship with the relief ports 59 and into engagement with the stop ring 63. The hydraulic fluid from the low pressure chamber 14 flows into the high pressure chamber via the gradually increasing orifice area at the piston head orifice 34 and also through the relief ports 59. In ,this manner the volume of the high pressure chamber 13 is maintained filled so that in the event of buff impact the cushion unit 10 is constantly able to provide the necessary resisting force. When the cushion unit returns to its fully extended position shown in FIG. l, the array of ports 43 in the piston rod are aligned with the elongated cylinder 46 so that the fluid from the dexible boot chamber 15 is free to ow into the piston rod 7 bore 37 via the annular openings 39, 47 and the array of ports 43.

Referring now to FIGS. through 8 there is shown another embodiment of reverse flow arrangement for precluding re-entry of hydraulic fluid into the flexible boot reservoir 15 during the return travel of the cushion device. As shown, the reverse flow arrangement is incorporated into the intermeidate cylinder head 23 and to this end the boss 64 may be formed as a separate member and fastened by insertion intermediate cylinder head 23 so that the inner end thereof extends slightly beyond the inner face. Fixed at one end to the inner face of the intermediate cylinder head- 23 and abutting a snap ring 66 spaced inwardly of the former at the other end is a tubular member 67 of which the outer diameter is substantially equal to the inner diameter of the cylinder bore 22. Radially spaced about the inner wall of the tubular member 67 are a plurality of guide members 68 which terminate at their forward end in a stop surface 69. Disposed about the tubular piston rod for movement between the stop surface 69 and the inwardly extending end of the boss 64 is an annularilat ring 70 having a flap 71 arranged between two of the guide members 68.

During contracting movement of the cushion unit from the neutral position as shown in FIG. 5 the pressure forces of the hydraulic fluid acting upon the flap 71 is operative to tilt the flap ring 70 angularly about the piston rod 36 so that friction is created therebetween. In this manner, movement ofthe piston head 27 and the piston rod 36 causes simultaneous movement of the flap ring frictionally held thereon so that the latter is displaced away from the annular opening 39 through the boss 64. Hydraulic fluid is then free to flow from the l-ow pressure chamber 14 to the flexible boot reservoir through the annular opening 39.

Upon return travel as viewed in FIG. 7 the flap ring 70 is tilted in the opposite direction as shown in the phantom line position so that the piston rod 36 is again operative to carry the latter rearwardly into overlying position with the inwardly extending end 65 of the boss 64. In this position the flap ring '70 blocks the annular opening 39 so that the fluid Within the low pressure chamber 14 is unable to return into the flexible boot reservoir 15.

In all other respects the operation of the relief port arrangement and the cushion unit is identical to that described above in connection with the embodiment of FIGS. 1 to 4.

What is claimed is:

1. A hydraulic cushioning device comprising ahydraulic fluid filled cylinder having a base plate closing one end thereof and an open end, an intermediate cylinder head disposed Within the bore of said cylinder inwardly of said open end to define `a boot chamber, hydraulic fluid passage means extending through said intermediate cylinder head, valve means disposable over said hydraulic fluid passage means, sa piston head reciprocable upon impact within said cylinder between a' neutral position adjacent ysaid cylinder head and a contracted position adjacent said closed end, said piston head defining a high pressure chamber With said closed end and a low pressure chamber with said intermediate cylinder head, a tubular piston rod fixed at lone end to said piston head and extending through said intermediate cylinder head outwardly of said open end, a second base plate closing said other end of said tubular piston rod, port means in said tubular piston rod adjacent said piston head providing hydraulic fluid communication between the piston rod bore and said low pressu-re chamber, metered orifice means through said piston head, a flexible boot reservoir disposed Within said boot chamber land fixed between said intermediate cylinder head and said outwardly end of said piston rod, said flexible boot being substantially-deflated in said neutral position of said piston head and being inflated upon receiving hydraulic fluid flowing through said hydraulic fluid passage means during travel from said neutral position t-o said contracted position, spring means disposed between said first and second base plates for returning said piston head from said contracted position to said neutral position and causing a reverse ow of said hydraulic fluid, said valve means coacting with said piston rod during travel of said piston head from said contracted position to said neutral position disposing said valve means over said fluid lpassage means for preventing fluid from reentering -said flexible boot reservoir. v

2. A hydraulic cushioning device comprising a hydraulic fluid filled cylinder having a base plate closing one end thereof and an open end, an intermediate cylinder head disposed within the bore of said 'cylinder inwardly of said open end to define a boot chamber, hydraulic uid passage measn extending through said intermediate cylinder head, valve means disposable over said hydraulic fluid passage means, a piston head -reciprocable upon impact within said cylinder between a neutral position adjacent -said cylinder head and a contracted position adjacent said closed end, said piston head defining a high pressure chamber with said closed end and a low pressure chamber with said intermediate cylinder head, a tubular piston rod fixed at one end to said piston head and extending through said intermediate cylinder head outwardly of said open end, a second base plate closing said other end of said tubular piston rod, port means in said tubular piston rod :adjacent said piston head providing hydraulic fluid communication between piston rod bore and said low pressure chamber, metered orifice means through said piston head, a flexible boot reservoir disposed within said boot chamber and fixed between said intermediate cylinder head and said outwardly end of said piston rod, said flexible boot being substantially deflated in said neutral -position of said piston head and being inflated upon receiving hydraulic fluid flowing through said hydraulic fluid passage means, during travel from said neutral position to :said contracted position, spring means disposed between said first and second ba-se plates for returning said piston head from said contracted position to said neutral position and causing a reverse flow of said hydraulic fluid, said valve means including spring means coacting with said piston rod during travel of said piston head from said contracted position to said neutral position disposing said valve means over said fluid passage means preventing fluid from re-entering said flexible boot reservoir.

3. The invention as defined in Vclaim 2 wherein said valve disc means comprises lan annular valve disc disposed about said piston r-od, and said spring means are fixed to said annular valve disc to resiliently embrace said piston lrod.

4. The invention as defined in claim 3 wherein said spring means comprises a plurality of resilient spring fingers.

5. A |hydraulic cushioning device comprising a hydraulic fluid filled cylinder having a base plate closing one end thereof and an open end, an intermediate cylinder head disposed within the bore of said cylinder inwar-dly of 'said open end to define a 'boot chamber, hydraulic -fluid passage means extending through said intermediate cylinder head, valve means disposable over said hydraulic fluid passage means, a piston head reciprocable upon impact within said cylinder between a 'neutral position adjacent said cylinder head and a contracted position adjacent said closed end, said piston head defining a high pressure'chamber with said closed end and a low pressure 'chamber with said intermediate cylinder, a tubular piston rod xed at one end to said piston head and extending through said intermediate cylinder head outwardly of said open end, a second base plate closing said other end of said tubular piston rod, port means in said tubular piston rod adjacent said piston head providing hydraulic fluid communication between the piston rod bore and said low pressure chamber, metered orice means through said piston head, a ilexible boot reservoir disposed within said boot chamber and fixed between said intermediate cylinder head and said outwardly end of said piston rod said flexible boot being substantially deilated in said neutral position of said piston head and being inflated upon receiving hydraulic fluid owing through said hydraulic fluid passage means during travel from said neutral to said contracted position, spring means disposed between said rst and second base plates for returning said piston head from said contracted position to said neutral position and causing a reverse iiow of said hydraulic fluid, said valve means being tiltable relative to and movable with said piston :rod during travel of said piston head between said contracted position to said neutral position and overlying said hydraulic fluid passage means to prevent uid from re-entering said exible boot reservoir during said travel to said neutral position.

6. The invention as defined in claim 5 wherein said valve means comprises an annular disc having an opening of greater diameter than said piston -rod so as to be tiltable thereabout.

7. rIhe invention as defined in claim 6 wherein said annular disc includes a flap extending lfrom a section of the periphery thereof.

8. The invention as dened in claim 7 wherein there are provided stop means disposed in the path of movement of said annular valve disc and which are spaced lengthwise from said fluid passage means on said intermediate cylinder head to limit lengthwise movement of said annular valve disc from said iluid passage means during said travel to said contracted position.

9. A hydraulic cushioning device comprising a hydraulic fluid filled cylinder |having a base plate closing one end thereof and an open end, an intermediate cylinder head disposed within the bore of said cylinder inwardly of said open end to dene a boot chamber, hydraulic lluid passage means extending through said intermediate cylinder head, valve means disposable over said hydraulic tluid passage means, a piston head reciprocable upon impact within said cylinder between a neutral position adjacent said cylinder head and a contracted position adjacent said closed end, said piston head dening a high pressure chamber with said closed end and a low pressure chamber with said intermediate cylinder head, a tubular piston rod fixed at one end to said piston head and extending through said intermediate cylinder head outwardly of said open end, a second base plate closing said other end of said tubular piston rod, port means in said tubular piston rod adjacent said piston head providing hydraulic ilu-id communication between the piston rod bore and said low pressure chamber, metered orifice means through said piston lhead, a flexible boot reservoir disposed within said boot chamber and fixed between said intermediate cylinder head and said` outwardly end of said piston rod, sai-d ilexible boot being substantially deflated in said neutral position of said piston head .and being inflated upon receiving hydraulic fluid flowing through said hydraulic fluid passage means during travel from said neutral position to said contracted position, spring means disposed between said tirst and second base plates for returning said piston head from said contracted position to said neutral position and causing a reverse flow of said hydraulic uid, said valve means coacting with said piston rod during travel of said piston head from said contracted position to said neutral position disposing said valve means over said fluid passage means to prevent hydraulic fiuid from re-entering said flexible 'boot reservoir, pressure relief ports extending through said piston head between said 'low pressure chamber and said high pressure chamber, and valve means on said piston head on the high lpressure face thereof closing-off iluid llow through said piston head during travel to said contracted position and being displaced away from said relief opening to permit hydraulic fluid flow therethrough during travel to said neutral position.

No references cited.

R. M. WOHLFARTH, Assistant Examiner.

ARTHUR L. LA POINT, Primany Examiner. 

1. A HYDRAULIC CUSHIONING DEVICE COMPRISING A HYDRAULIC FLUID FILLED CYLINDER HAVING A BASE PLATE CLOSING ONE END THEREOF AND AN OPEN END, AN INTERMEDIATE CYLINDER HEAD DISPOSED WITHIN THE BORE OF SAID CYLINDER INWARDLY OF SAID OPEN END OF DEFINE A BOOT CHAMBER, HYDRAULIC FLUID PASSAGE MEANS EXTENDING THROUGH SAID INTERMEDIATE CYLINDER HEAD, VALVE MEANS DISPOSABLE OVER SAID HYDRAULIC FLUID PASSAGE MEANS, A PISTON HEAD RECIPROCABLE UPON IMPACT WITHIN SAID CYLINDER BETWEEN A NEUTRAL POSITION ADJACENT SAID CYLINDER HEAD AND A CONTRACTED POSITION ADJACNET SAID CLOSED END, SAID PISTON HEAD DEFINING A HIGH PRESSURE CHAMBER WITH SAID CLOSED END AND A LOW PRESSURE CHAMBER WITH SAID INTERMEDIATE CYLINDER HEAD, A TUBULAR PISTON ROD FIXED AT ONE END TO SAID PISTON HEAD AND EXTENDING THROUGH SAID INTERMEDIATE CYLINDER HEAD OUTWARDLY OF SAID OPEN END, A SECOND BASE PLATE CLOSING SAID OTHER END OF SAID TUBULAR PISTON ROD, PORT MEANS IN SAID TUBULAR PISTON ROD ADJACENT SAID PISTON HEAD PROVIDING HYDRAULIC FLUID COMMUNICATION BETWEEN THE PISTON ROD BORE AND SAID LOW PRESSURE CHAMBER, METERED ORIFICE MEANS THROUGH SAID PISTON HEAD, A FLEXIBLE BOOT RESERVOIR DISPOSED WITHIN SAID BOOT CHAMBER AND FIXED BETWEEN SAID INTERMEDIATE CYLINDER HEAD AND SAID OUTWARDLY END OF SAID PISTON ROD, SAID FLEXIBLE BOOT BEING SUBSTANTIALLY DEFLATED IN SAID NEUTRAL POSITION OF SAID PIS TON HEAD AND BEING INFLATED UPON RECEIVING HYDRAULIC FLUID FLOWING THROUGH SAID HYDRAULIC FLUID PASSAGE MEANS DURING TRAVEL FROM SAID NEUTRAL POSITION TO SAID CONTRACTED POSITION, SPRING MEANS DISPOSED BETWEEN SAID FIRST AND SECOND BASE PLATE FOR RETURNING SAID PISTON HEAD FROM SAID CONCENTRATED POSITION TO SAID NEUTRAL POSITION AND CAUSING A REVERSE FLOW OF SAID HYDRAULIC FLUID, SAID VALVE MEANS COACTING WITH SAID PISTON ROD DURING TRAVEL OF SAID PISTON HEAD FROM SAID CONTRACTED POSITION TO SAID NEUTRAL POSITION DISPOSING SAID VALVE MEANS OVER SAID FLUID PASSAGE MEANS FOR PREVENTING FLUID FROM REENTERING SAID FLEXIBLE BOOT RESERVOIR. 